As the processing power, data capacity, and functionality of personal computers and computer systems have increased, personal computers interconnected with other personal computers and higher-end computer systems have become a major medium for transmission of a variety of different types of information and entertainment, including music. Users of personal computers can download a vast number of different, digitally encoded musical selections from the Internet, store digitally encoded musical selections on a mass-storage device within, or associated with, the personal computers, and can retrieve and play the musical selections through audio-playback software, firmware, and hardware components. Personal computer users can receive live, streaming audio broadcasts from thousands of different radio stations and other audio-broadcasting entities via the Internet.
As users have begun to accumulate large numbers of musical selections, and have begun to experience a need to manage and search their accumulated musical selections, software and computer vendors have begun to provide various software tools to allow users to organize, manage, and browse stored musical selections. For both musical-selection storage and browsing operations, it is frequently necessary to characterize musical selections, either by relying on text-encoded attributes, associated with digitally encoded musical selections by users or musical-selection providers, including titles and thumbnail descriptions, or, often more desirably, by analyzing the digitally encoded musical selection in order to determine various characteristics of the musical selection. As one example, users may attempt to characterize musical selections by a number of music-parameter values in order to collocate similar music within particular directories or sub-directory trees and may input music-parameter values into a musical-selection browser in order to narrow and focus a search for particular musical selections. More sophisticated musical-selection browsing applications may employ musical-selection-characterizing techniques to provide sophisticated, automated searching and browsing of both locally stored and remotely stored musical selections.
The tempo of a played or broadcast musical selection is one commonly encountered musical parameter. Listeners can often easily and intuitively assign a tempo, or primary perceived speed, to a musical selection, although assignment of tempo is generally not unambiguous, and a given listener may assign different tempos to the same musical selection presented in different musical contexts. However, the primary speeds, or tempos, in beats per minute, of a given musical selection assigned by a large number of listeners generally fall into one or a few discrete, narrow bands. Moreover, perceived tempos generally correspond to signal features of the audio signal that represents a musical selection. Because tempo is a commonly recognized and fundamental music parameter, computer users, software vendors, music providers, and music broadcasters have all recognized the need for effective computational methods for determining a tempo value for a given musical selection that can be used as a parameter for organizing, storing, retrieving, and searching for digitally encoded musical selections.